In this application we are requesting funds to purchase and install an X-RAD 320 Biological Irradiator for the University of Southern California Keck School of Medicine. This machine can expose both cells in culture and small animal to x-rays in the energy range 50 to 320 Kvp. In the configuration requested the dose rate can be varied, the energy of the x- rays can be varied and the machine has a variable collimator to allow for partial body radiation. It is intended that this machine will eventually replace an aging AECL cesium gamma irradiator that has been in use at the School of Medicine since 1983. The current cesium irradiator has a single dose rate that is gradually degrading and can only do total body exposures. It has only an analog dose-timing device and cannot time less than a 6 second exposure. Due to its age there is an increasing number of breakdowns and these lead to significant downtime. Cesium irradiators are considered a risk by Homeland Security and as such Radiation Safety has to spend significant resources making sure it is safe, protected and in compliance with current regulations. The new irradiator only produces x-rays when switched on and is thus not considered a radiation threat. Currently there are more than one hundred users of the cesium machine. Many are funded by NIH grants as well as other federal agencies. Many of these studies are difficult to do on the cesium irradiator because it can only do exposures larger than about 10 cGy and whole body radiation. Some funded grants are using facilities off-site as far away as San Diego (150 miles from Los Angeles). The new irradiator will be installed in the basement of the Eli and Edythe Broad Institute for Regenerative Medicine on the same level as animal facilities to afford easy access for animal studies. The Broad Institute is under construction and expected to open in April of 2010. The P.I Dr Colin Hill of the Radiation Oncology Department in the Norris Comprehensive Cancer Center has put together an experienced management team and management plan to install and operate this new machine that includes members of the Radiation Oncology Department and the USC Radiation Safety Office.